Cognitive radio is an intelligent radio that can be programmed and configured dynamically. The transceivers are designed to use the best wireless channels in their vicinity. Such radio transceivers automatically detect available channels in wireless spectrum, then accordingly change their transmission or reception parameters to allow more concurrent wireless communications in a given spectrum band at one location. This process is a form of dynamic spectrum management.
The cognitive radio main principle lies in sounding the radio environment in order to find the best resource for transmission. This is only possible if the radio environment doesn't change between the sounding and transmission period. When a telecommunication device moves, its radio environment changes quickly which does not allow using a cognitive radio approach.
Cognitive radio finds application in moving systems like for example communications-based train control (CBTC) system. Communications-based train control systems make use of the telecommunications between the train and track equipment for the traffic management and infrastructure control. By means of the CBTC systems, the exact position of a train may be known more accurately than with traditional signalling systems. This results in a more efficient and safer way to manage the railway traffic. Metros and other railway systems are able to improve headways while maintaining or even improving safety.